1. Field of the Invention
This invention relates generally to a method and system for use in optical fiber technology. More particularly, this invention relates to a method and apparatus for manufacturing an improved dual fiber optical collimator.
2. Description of the Prior Art
As optical fiber technology is being more broadly applied in the telecommunications, data communications and CATV industries, the fiber optic component industry is now confronted with increasing requirement for high reliability of fiber optic components. Currently, most of in-line fiber optic components are designed and manufactured based on optical collimators which provide low-loss light transmission from the input fiber to the output fiber through an optical element. As a basic building block of the fiber optic components, the reliability and level of performance of the fiber optic components depend heavily on the reliability and the performance characteristics of the optical collimators. Dual-fiber optical collimators are one type of collimators most widely employed in making the fiber optic components. For example, dual-fiber optical collimators are employed to make thin film filter based wavelength division multiplexers, hybrid optical isolators, and compact optical circulators.
FIG. 1 shows the structure of a typical dual-fiber optical collimator that includes a dual-fiber pigtail, a GRIN lens, a glass tube and a stainless steel holder. In a typical manufacturing process, a GRIN lens 15 and a dual fiber pigtail 30 are mounted on an alignment stage (not shown). The relative position of the GRIN lens 15 and the fiber pigtail 30 is adjusted to achieve a lowest transmission loss between the input fiber 20 and output fiber 25. Then the fiber pigtail 30 is fixed to the GRIN lens 15 at that position by applying an ultraviolet (UV) curing epoxy 35. An example of the UTV curing epoxy is MODEL ELC4481 from ElectrouLnte Company in Danbury, Conn. Then the fiber pigtail 30 is fixed to a glass tube 40 by applying an UV curing epoxy 45 and the glass tube 40 is fixed to a stainless steel holder 50 by a heat-curing epoxy 55. The stainless steel holder is gold-plated and applied for the purpose of soldering. The UV curing epoxy 35 is also filling the gap between the GRIN lens 15 and the stainless steel holder 50. While the method and system provides a dual-fiber optical collimator with good performance and its reliability is suitable for many types of applications until now. The dual-fiber optical collimators manufactured according to the above mentioned method however fail and perform poorly when they are implemented in fiber optic components that demand long term operation in a high temperature, e.g., 85.degree. C., and high humidity, e.g., 85% humidity, environment The UV curing epoxy bonding, e.g, epoxy 35 and 45, are often broken when subject to such operation conditions and then the bond breakage results in poor optical signal transmission. Furthermore, the UV curing epoxy bonding 35 is also often deformed during the soldering process because it is in contact with the stainless steel holder and the soldering temperature is pretty high. This bonding deformation causes significantly poor optical signal transmission. Thus, further development of reliable fiber-optic components with high level of performance is limited by these difficulties.
Therefore, a need still exists in the art of design and manufacture of dual-fiber optical collimators to provide new material compositions, device structure, and manufacture processes to overcome the difficulties discussed above. Specifically, a technique to provide the collimators with higher reliability for long term operation in high temperature and humidity environment is required. Since production costs have been an important contributing factor prohibiting practical implementation of fiber-optical technology, it is also highly desirable that the cost of such technology would be as low as possible.